Americans represent 5% of the world's population but drive almost a third of its cars, which in turn account for nearly half the carbon dioxide pumped out of exhaust pipes into the atmosphere each year. American cars are also less fuel efficient than passenger vehicles elsewhere, emitting 15% more carbon dioxide, and are driven further across America's wide open spaces, said a report by the Environmental Defence watchdog group.
With suburban sprawl far outpacing the growth of public transport networks, Americans are commuting more each year, shopping more, and driving further to the shops each time. Between 1990 and 2001 the number of kilometres travelled on American shopping trips rose by 40%.